1. Field of the Invention
The present invention is related to a method of making low-profile wire connection between a first bonding pad in a semiconductor device and a second bonding pad. More particularly, the present invention relates to the automatic wire bonder moving its capillary bonding tool in a predetermined path.
2. Description of the Related Art
A conventional method of making wire connection includes a wire electrically connecting a first bonding pad and a second bonding pad to form a closed loop in a semiconductor device. The wire extends upward from the first bonding pad and downward to the second bonding pad, so that the wire has a high profile between the first bonding pad and the second bonding pad. Because the high profile is mechanically supported only at the point of the bonding pad, the high profile can easily be shifted by stress. When the semiconductor device is in the molding process, the liquified encapsulant material pushes the wires, which can easily to be shifted, and wire sweeping occurs.
U.S. Pat. No. 4,932,584, issued on Jun. 12, 1990 to Yamazaki et al., discloses a method of making wire connection. As shown in FIG. 1, after a wire 110 is connected to a first bonding pad 120, a capillary 100 is moved straight up an appropriate length. As shown in FIG. 2, the capillary 100 is then moved away from a second bonding pad (not shown) thus making a first reverse action to bend the wire 110 at an appropriate angle. From there, as shown in FIG. 3, the capillary 100 is again raised an appropriate length. As shown in FIG. 4, and an action is performed to bend the wire 110 at an appropriate angle, so that the capillary 100 is moved again in the direction of the second bonding pad. As shown in FIG. 5, the capillary 100 is further raised a predetermined distance by feeding out the wire 110 to a length which is enough to make a wire loop, and then the capillary 100 is moved down to the second bonding pad 130 where bonding is performed.
U.S. Pat. No. 5,111,989, issued on May 12, 1992 to Holdgrafer et al., discloses a method of making low-profile fine-wire interconnection. A method of making lowprofile slack-free fine-wire interconnections between a first bonding point on a semiconductor chip and a seconding bonding point on a lead frame lead comprising the steps of: bonding the end of fine wire to the pad of a semiconductor chip at a first bonding point employing a bonding tool mounted in a automatic wire bonder, raising the bonding tool to payout a total predetermined length of wire which is slightly smaller than the amount of wire required for a final wire interconnection, closing the wire clamps of the automatic wire bonder to prevent movement of the fine wire through the capillary bonding tool, moving the bonding tool horizontally and vertically toward an artificially generated second bonding point on a lead frame lead to create a conventional low loop height interconnection fine wire loop leaving a wire curl extending from the bonding tool, applying a first bonding force to the bonding tool that is sufficient to effect a secondary bond and is also sufficient to reduce the cross section of the fine wire at the artificially generated second bonding point, simultaneously moving the capillary bonding tool toward the second bonding point while mashing the fine wire between the lead frame lead and the working face of the moving bonding tool, reducing the loop height of said fine wire interconnection by applying a pull-down tension force on the conventional low loop by clamping the fine wire and moving the bonding tool to the second bonding point, and applying a second bonding force and ultrasonic energy to the bonding tool at the second bonding point for generating a second bond.
U.S. Pat. No. 5,156,323, issued on Oct. 20, 1992 to Kumazawa et al., discloses a wire bonding method. After a wire is connected to a first bonding point, a capillary is moved straight up and then the capillary moved away from a second bonding point (not shown) thus making the first reverse action. From there, the capillary is again raised and a second reverse action is performed so that the capillary is moved again in a direction opposite to the second bonding point. The capillary is further raised by feeding out the wire to a length which is enough to make a wire loop, and then the capillary is moved down to the second bonding point where the bonding is performed.
Neither U.S. Pat. No. 4,932,584 nor U.S. Pat. No. 5,156,323 discloses a wire connection with a sufficiently low profile so as to reduce the occurrence of wire sweeping. U.S. Pat. No. 5,111,989 discloses simultaneously mashing, forward extruding and wire drawing the fine wire under the working face of the capillary bonding tool while moving away from the first ball bond to the second bond target position. Excessive tension in the wire would create stress in the bend above the ball which is formed a neck being weakened or work hardened. However, the capillary bonding tool moving away from the first ball pad to the second bond target position pulls the neck of the ball which is still easily broken, so that reduces the reliablity of wire connection.
The present invention intends to provide a method of making low profile wire connection in such a way as to mitigate and overcome the above problem.